1. Field of the Invention
The present invention relates to an oxide superconducting conductor, and more particularly, it relates to an oxide superconducting conductor having a high critical current density.
2. Description of the Background Art
In recent years, ceramic superconducting materials, i.e., oxide superconducting materials, exhibiting higher critical temperatures are watched with interest. In particular, yttrium, bismuth and thallium oxide superconducting materials exhibit high critical temperatures of about 90 K, 110 K and 120 K respectively, to remain in superconducting states under temperatures higher than the liquid nitrogen temperature. Thus, such oxide superconducting materials are expected for practical application to high temperature superconducting materials with cooling media of liquid nitrogen.
In relation to practical use of such an oxide superconducting material, study is now being made on application to a superconducting cable which is cooled with liquid nitrogen, for example. When a superconducting cable consisting of an oxide superconducting material is put into practice, it is possible to simplify a thermal protection system and to reduce the cooling cost since this cable requires no cooling with high-priced liquid helium, dissimilarly to a conventional superconducting cable utilizing a metal superconducting conductor.
The inventors have satisfied in development of an oxide superconducting wire which is excellent in bendability by bringing a superconductor into a multifilamentary state with silver, for example, as an exemplary oxide superconducting conductor which is applied to such a superconducting cable. They have discovered that it is possible to obtain a flexible oxide superconducting conductor having a high critical current density by assembling a plurality of such silver-covered superconducting multifilamentary wires on a flexible pipe which serves as a core called a former.
In an oxide superconducting conductor obtained in the aforementioned manner, however, there still remains a room to be improved in view of the critical current density. An oxide superconducting conductor which is applied to a cable or the like must have a higher critical current density.